Method and device for manufacturing saw wire

ABSTRACT

[Object] 
     To provide a method and device for manufacturing an abrasive grain-fixed saw wire that realize homogeneous distribution of abrasive grains adhered to the outer surface of a wire while suppressing variations in the amount of abrasive grains adhered to the outer surface of the wire, even in a high-efficiency wire feeding mode with a high density of abrasive grains, back-and-forth running of the wire, and the like. 
     [Constitution] 
     The present invention includes: a plating tank  16 A that stores a plating solution M 1  containing abrasive grains D; a wire feeding means  2  that lets a wire W pass through the plating solution M 1;  an electric current supply means  3  that supplies an electric current to the wire W and the plating solution M 1;  an abrasive grain amount calculation means  4  that calculates the amount of abrasive grains D adhered to the outer surface of the wire W having passed through the plating solution M 1;  and an electric current control means  5  that increases or decreases the value of an electric current flown into the wire W in the plating solution M 1  by the electric current supply means  3  according to the calculated amount of abrasive grains to control variations in the amount of the abrasive grains adhered to the outer surface of the wire so as to fall within a predetermined range.

TECHNICAL FIELD

The present invention relates to methods and devices for manufacturing abrasive grain-fixed saw wires for use in the processes of slicing various electronic materials typified by single-crystal silicon or the like.

BACKGROUND ART

Abrasive grain-fixed saw wires for use in the processes of slicing various electronic materials are formed by fixing abrasive grains of diamond, CBN, or the like, onto the outer peripheries of the wires. Methods used to fix diamond include resin bonding and electrodeposition by which abrasive grains are fixed by electroplating. The resin bonding method has a drawback of providing a shorter life of a wire because resin is weak in force of holding abrasive grains. The electrodeposition method provides a longer life of a wire but has a drawback of decreasing productive efficiency (production speed is low and wider space is necessary).

To improve productivity of the electrodeposition method, there has been adopted an approach in which as much amount of abrasive grains as possible is contained in high density in a plating solution, the running speed of a wire is increased, and an auxiliary electrode is provided to maintain electric current density (for example, refer to Patent Document 1). There is another approach by which a wire is passed through a flow of a plating solution with abrasive grains dispersed, along the direction of the flow, thereby to adhere the abrasive grains efficiently to the wire (refer to Patent Document 2).

When high-density abrasive grains are included in a plating solution, the production efficiency can be significantly improved with higher production speed, cost reduction, and the like. However, the amount of abrasive grains adhered to the outer surface of a wire varies largely on the degree of dispersion of abrasive grains in the plating solution, influence of plating efficiency, and the like, and thus the wire may have densely adhered portions and sparsely adhered portions. Therefore, it is difficult to adhere and distribute abrasive grains evenly to the outer surface of the wire in a stable manner.

Further, the amount of precipitated plating is influenced by the immersed surface area, electric current density, and immersion time. Thus, to short the immersion time for enhancement of productivity, it is necessary to increase the immersed surface area or the electric current density as much as possible. However, when the electric current value is increased to raise the electric current density, the wire generates heat and thus may be broken. Meanwhile, when the immersed surface area is increased, the electric current density tends to decrease, and it is necessary to use a larger plating tank and increase the amount of plating solution, which causes a problem with production costs. To assure the sufficient immersion surface area with the foregoing technique disclosed in Patent Document 1, it is also necessary to store a plating solution in a large plating tank and provide an auxiliary electrode separately from a main electrode, and thus there is room for improvement in productivity and production costs.

CITATION LIST Patent Literatures Patent Document 1: JP-A No. 2006-55952 Patent Document 2: JP-A No. 2006-110703 DISCLOSURE OF THE INVENTION Technical Problem

In light of the foregoing problems, an object of the present invention is to provide a method and device for manufacturing an abrasive grain-fixed saw wire that realize homogeneous distribution of abrasive grains adhered to the outer surface of a wire while suppressing variations in the amount of abrasive grains adhered to the outer surface of the wire, even in a high-efficiency wire feeding mode with a high density of abrasive grains and the like, and achieve improvements in productivity and production costs.

Solution to Problem

To solve the foregoing issue, the present invention provides a method for manufacturing an abrasive grain-fixed saw wire by which a wire is passed through a plating solution containing abrasive grains to fix the abrasive grains to the outer periphery of the wire by electroplating, wherein the amount of the abrasive grains adhered to the outer surface of the wire having passed through the plating solution is calculated, and based on the calculated amount of the abrasive grains, the value of an electric current flown into the wire in the plating solution is increased or decreased to control variations in the amount of abrasive grains adhered to the outer surface of the wire so as to fall within a predetermined range.

In this arrangement, it is preferred that, after forming the wire with the abrasive grains adhered to the outer surface by electroplating via a first plating layer, the wire is passed through a plating solution without abrasive grains to form a second plating layer on the outer surface by electroplating.

It is preferred in particular that the first plating layer for adhering the abrasive grains to the outer surface of the wire is configured to be thinner than the second plating layer.

It is also preferred that the outer surface of the wire having passed through the plating solution is imaged by a camera, and the amount of the abrasive grains is calculated based on image information in the taken image.

It is also preferred that the wire is routed around a plurality of times between an out-solution rotary roller that is disposed outside the plating solution and supplied with an electric current by an electric current supply means and an in-solution rotary roller that is disposed in the plating solution, and the wire is run back and forth a plurality of times between inside and outside of the plating solution.

It is preferred in particular that the wire is routed around at least two in-solution rotary rollers disposed in the plating solution.

It is further preferred that a guide groove for guiding the wire a plurality of times in the direction of roller circumference, is provided on the outer peripheral surface of the out-solution rotary roller and/or the in-solution rotary roller.

It is also preferred that the plating solution is stirred by a stirring means disposed in the plating solution.

The present invention is also configured as a device for manufacturing an abrasive grain-fixed saw wire that lets a wire pass through a plating solution containing abrasive grains to fix the abrasive grains to the outer periphery of the wire by electroplating, comprising: a plating tank that stores the plating solution containing the abrasive grains; a wire feeding means that lets the wire pass through the plating solution; an electric current supply means that supplies an electric current to the wire and the plating solution; an abrasive grain amount calculation means that calculates the amount of abrasive grains adhered to the outer surface of the wire having passed through the plating solution; and an electric current control means that increases or decreases the value of an electric current flown into the wire in the plating solution by the electric current supply means according to the amount of abrasive grains calculated by the abrasive grain amount calculation means to control variations in the amount of the abrasive grains adhered to the outer surface of the wire so as to fall within a predetermined range.

In this arrangement, it is preferred that the abrasive grain amount calculation means includes a camera that images the outer surface of the wire having passed through the plating solution and a computing means that calculates the amount of the abrasive grains based on image information in an image taken by the camera.

It is also preferred that the device includes an out-solution rotary roller that is disposed outside the plating solution and supplied with an electric current by an electric current supply means and an in-solution rotary roller that is disposed in the plating solution, wherein the wire is routed around a plurality of times between the out-solution rotary roller and the in-solution rotary roller and is run back and forth a plurality of times between inside and outside of the plating solution.

Advantageous Effects of Invention

According to the invention of the subject application described above, abrasive grains, specifically, abrasive grains coated with conductive metal films are electrically charged in the plating solution, and when the value of an electric current is increased, a coulomb force becomes larger to facilitate adhesion of the abrasive grains to the outer surface of the wire, whereas when the value of an electric current is decreased, a coulomb force becomes smaller to make the abrasive grains less prone to adhere to the outer surface of the wire. This makes it possible to adjust and control variations in the amount of abrasive grains adhered to the outer surface of the wire so as to fall within a predetermined range. That is, even when the degree of dispersion of abrasive grains in the plating solution or the plating efficiency or the like is decreased due to the high density of the abrasive grains, the back-and-forth running of the wire or the like, it is possible to suppress variations in the amount of abrasive grains adhered to the outer surface of the wire and achieve homogenous distribution of the adhered abrasive grains.

It is not thinkable from general common technical knowledge in electroplating to increase or decrease the value of an electric current that causes a plating layer to vary in thickness and property. The present invention is configured to purposely increase or decrease the value of an electric current to solve the conventionally unsought issue of homogenous distribution of adhered abrasive grains, but it is not evitable to eliminate variations of a plating layer in thickness and property. In the present invention, nevertheless, the value of an electric current is increased or decreased as described above to let abrasive grains adhere to the outer surface of the wire via the first plating layer, and then the wire is passed through a plating solution without abrasive grains to form the second plating layer on the outer surface by electroplating. The second plating layer makes relatively smaller influence of the variations in the first plating layer on the whole, thereby to maintain the quality of the plating layers. In addition, it is possible to fix abrasive grains to the wire in a reliable manner. The foregoing configuration is effective in the case where a wire is passed through a plating solution containing abrasive grains to fix the abrasive grains tentatively to the wire and then the wire is passed through a plating solution without abrasive grains to fix the abrasive grains in a reliable manner.

In particular, the first plating layer under influence of the variations is made thinner than the second plating layer, which makes it possible to further reduce the degree of the relative influence and obtain a high-quality plating layer on the whole.

Since the outer surface of the wire having passed through the plating solution is imaged by the camera and the amount of abrasive grains is calculated based on the image information in the taken image, it is possible to calculate the accurate amount of abrasive grains adhered to the outer surface of the wire.

Since the wire is routed around a plurality of times between the out-solution rotary roller that is disposed outside the plating solution and supplied with an electric current by the electric current supply means and the in-solution rotary roller that is disposed in the plating solution, and the wire is run back and forth between inside and outside of the plating solution, the wire is supplied with an electric current by the electric current supply means via the out-solution rotary roller during each back-and-forth run between the out-solution rotary roller and the in-solution rotary roller, and it is thus possible to maintain the electric current density without excessively increasing the amount of an electric current and increase the immersed surface area in an exponential manner. This raises significantly the production speed. For example, when a pair of electrodes is provided only at both ends of a plating solution-immersed portion of one wire and the value of an electric current to be applied to the wire is set as a reference value, it is possible to apply an electric current of the reference value to each row of wires arranged in parallel between the rotary rollers and apply an electric current of the value twice the number of back-and-forth runs. In addition, since the wire is routed around between the rotary rollers and run back and forth a plurality of times, it is possible to eliminate the need for providing separately a main electrode and an auxiliary electrode and reduce significantly the volume of the plating solution (the plating tank). Accordingly, it is possible to provide a sufficient production space and decrease significantly the used amount of the plating solution, thereby resulting in a considerable decrease in production costs.

Since the wire is routed around the at least two in-solution rotary rollers in the plating solution, it is possible to disperse a stress applied to the wire and run the wire in a more stable manner. As a result, it is possible to increase the running speed of the wire and thus further improve the production speed by adjusting the number of back-and-forth runs as appropriate.

Since the guide groove is provided to guide the wire a plurality of times in the direction of roller circumference, on the outer peripheral surface of the out-solution rotary roller and/or the in-solution rotary roller, it is possible to further enhance running stability of the wire and increase the running speed of the wire, thereby achieving improvement in the production speed.

Since the plating solution is stirred by the stirring means in the plating solution, it is possible to improve dispersibility of abrasive grains existing in the plating solution and achieve homogenous adhesion of abrasive grains to the surface of the wire.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative diagram showing an entire configuration of a saw wire manufacturing device according to a typical embodiment of the present invention;

FIG. 2 is an illustrative diagram showing a configuration of main components in the saw wire manufacturing device;

FIG. 3 is a block diagram showing a control computer constituting the saw wire manufacturing device;

FIG. 4 (a) is an illustrative diagram showing a region of a wire with abrasive grains imaged by a camera, and FIGS. 4 (b) to 4 (d) are illustrative diagrams showing examples of acquired image information;

FIG. 5 is an illustrative diagram showing conversions of the image information to shape recognition data;

FIG. 6 is an illustrative diagram showing a configuration of main components of a saw wire manufacturing device according to a typical embodiment of the present invention;

FIG. 7 is a schematic side view of a modification example of a layout of rotary rollers;

FIG. 8 is a schematic side view of another modification example of a layout of the rotary rollers;

FIG. 9 is a perspective view of the modification example of a layout of the rotary rollers;

FIG. 10 is a schematic side view of a further another modification example of a layout of the rotary rollers; and

FIG. 11 is an illustrative diagram showing a rotary roller.

REFERENCE SIGNS LIST

-   1 Manufacturing device -   2 Wire feeding means -   3 Electric current supply means -   4 Abrasive grain amount calculation means -   5 Electric current control means -   6 Control computer -   7 Guide groove -   10 Feeding machine -   11 Alkali tank -   12 Water washing tank -   13 Acid tank -   14 Water washing tank -   16A First plating tank -   16B Second plating tank -   17 Water washing tank -   18 Winding machine -   20, 20 a, and 20 b Rotary roller -   21, 21 a, and 21 b Rotary roller -   22 Stirring blade -   30 Power feeding device -   31 Anode -   40 Camera -   60 Processing device -   60 a Image information acquisition processing part -   60 b Abrasive grain amount calculation processing part -   60 c Determination processing part -   60 d Electric current control processing part -   61 Storage means -   61 a Image information storage part -   62 Region -   D Abrasive grain -   M1 Plating solution -   M2 Plating solution -   W Wire -   m1 Plating layer

DESCRIPTION OF EMBODIMENTS

Next, embodiments of the present invention will be described below in detail with reference to the attached drawings.

As shown in FIG. 2, a saw wire manufacturing device 1 of the present invention is an abrasive grain-fixed saw wire manufacturing device that is configured to let a wire W pass through a plating solution M1 containing abrasive grains D to fix (electrodeposit) the abrasive grains D to the outer periphery of the wire W by electroplating, the device 1 includes at least: a plating tank 16A that stores the plating solution M1 containing the abrasive grains D; a wire feeding means 2 that lets the wire W pass through the plating solution M1; an electric current supply means 3 that supplies an electric current to the wire W and the plating solution M1; an abrasive grain amount calculation means 4 that calculates the amount of the abrasive grains D adhered to the outer surface of the wire W having passed through the plating solution M1; and an electric current control means 5 that increases or decreases the value of an electric current flown into the wire W in the plating solution M1 by the electric current supply means 3 according to the calculated amount of the abrasive grains, thereby to control variations in the amount of the abrasive grains adhered to the outer surface of the wire so as to fall within a predetermined range.

FIG. 1 is an illustrative diagram showing an entire configuration of the saw wire manufacturing device 1 according to the present invention. In this example, arranged in order from a feeding machine 10 feeding the wire W along the running direction of a wire 6 are: an alkali tank 11 for subjecting the wire to alkali degreasing; a water washing tank 12 for water-washing the wire; an acid tank 13 for subjecting the wire to acid pickling; a water washing tank 14 for water-washing the wire; a first plating tank 16A for adhering tentatively abrasive grains to the outer periphery of the wire; a second plating tank 16B for forming a second plating layer on the outer surface of the wire; a water washing tank 17; and a winding machine 18. The thus obtained saw wire is used in various applications.

There is no particular limit to the composition of a plating solution containing abrasive grains in the first plating tank 16A, but any plating solution of general component composition for use in fixing abrasive grains by electroplating can be used. For example, the plating solution may contain nickel-containing organic acid, nickel-containing inorganic acid, or the like, but is not limited to this. The plating solution may be provided as appropriate with a brightening agent, a pH buffer, or the like. The plating solution in the second plating tank 16B may also be of any conventionally public-known composition. The major component of the plating solution in the second plating tank 16B is preferably the same as the plating solution in the first plating tank 16A.

The abrasive grains contained in the plating solution may be superabrasive grains of diamond, CBN, or the like, for example, but are not limited to this. There is no particular limit to the particle size of the abrasive grains as far as the abrasive grains can be used for saw wires, but the abrasive grains of diamond may be preferably 5 to 100 μm, for example. The surfaces of the abrasive grains are coated with metal films. There is no particular limit to the wire W but the wire W may be formed by metal, non-metal, or various other materials. The metal materials include tungsten wire, piano wire, dies steel tempered at a temperature of 400° C. or more, high-speed steel, stainless steel, and the like. The non-metal materials include carbon fiber, aramid fiber, alumina fiber, boron fiber, silicon carbide fiber, and the like. In the case of using any non-metal wire, the wire is preferably subjected to a general plating process to make the surface of the wire conductive.

This example is configured to subject the wire to double plating in the first plating tank 16A and the second plating tank 16B as shown in FIG. 1. Alternatively, the second plating tank may be omitted such that the wire is plated only in the first plating tank. Besides, the structure, layout, selection, and combination of the plating tanks are not limited to this example, but it is possible to use widely conventionally public-known modes for saw wire manufacturing devices configured to fix abrasive grains by electroplating. In this example, as described below, the saw wire manufacturing device is configured in such a manner that the wire is routed around a plurality of times between the rotary rollers inside and outside the solution and is run back and forth, so that the wire is fed and supplied with an electric current in the first and second plating tanks 16A and 16B. Alternatively, it is possible as a matter of course to use any of conventionally public-known configurations other than the foregoing one.

As shown in FIGS. 2 and 6, an out-solution rotary roller 20 and an in-solution rotary roller 21 are disposed in the first plating tank 16A, and the wire W fed through the water washing tank 14 is routed around a plurality of times between the rotary rollers 20 and 21 inside and outside the plating solution and run back and forth a plurality of times between the inside and outside of the plating solution M1. Accordingly, the abrasive grains D are adhered to the outer periphery of the wire W, and then the wire W is fed to the second plating tank 16B. In this example, as shown in FIG. 6, the wire W is wound around the two rotary rollers 20 and 21 in a spiral form (the two rotary rollers 20 and 21 are located inside a spiral formed by the wire W) and run back and forth a plurality of times between the inside and outside of the plating solution M1. The rotary rollers 20 and 21 function as a wire feeding means 2 together with the feeding machine 10 and the winding machine 18.

The rotary rollers 20 and 21 are parallel to each other and parallel to the liquid level of the plating solution M1 in the axial direction. Disposed in the plating solution are a stirring blade 22 stirring the plating solution M1 and anodes 31 in parallel with the wire W running back and forth. The rotary roller 20 and the anodes 31 are each connected to a power feeding device 30 such that an electric current is supplied to the wire W through the outer peripheral surface of the rotary roller 20. In this example, loops of the wire W running back and forth between the rotary rollers 20 and 21 constitute cathodes, and the abrasive grains D are adhered to the outer peripheral part of the wire W via a plating film in the vicinity of the anodes 31. That is, the rotary roller 20 serves as an electric current supply means 3 together with the power feeding device 30 and the anodes 31.

In this example, the wire W is wound and run in a spiral form around the two rotary rollers 20 and 21 inside and outside the plating solution M1. Alternatively, the wire W may be routed so as to pass transversely, that is, cut a figure of eight between the rotary rollers 20 and 21. There may be provided three rotary rollers around which the wire W is routed. To bring the wire W into electric conduction, the rotary roller 20 serving as electric current supply means 3 may be entirely formed by a conductive material or may include a conductive material at an outer peripheral portion contacting the wire W. The conductive material may be a metal, a conductive polymer, or the like.

FIG. 7 shows a modification example of a layout of the rotary rollers. In this example, two or more in-solution rotary rollers 21 a and 21 b are disposed in the plating solution. This makes it possible to disperse a stress applied to the wire W to achieve more stable running of the wire. In this example, one out-solution rotary roller 20 is disposed outside the plating solution M1 containing abrasive grains, and the two rotary rollers 21 a and 21 b are disposed in the plating solution M1. In a lateral view of these rollers, the out-solution rotary roller 20 has a center of a rotation axis located on a perpendicular bisector of a line connecting centers of rotation axes of the two in-solution rotary rollers 21 a and 21 b.

The rotary rollers are axially parallel to each other and parallel to the liquid level of the plating solution. The wire W is routed around a plurality of times between the out-solution roller 20 and the in-solution rotary rollers 21 a and 21 b and is run back and forth a plurality of times between the inside and outside of the plating solution M1. More specifically, the wire W is wound around the three rotary rollers such that the rotary rollers are located inside a spiral formed by the wire W, and is run back and forth a plurality of times between the inside and outside of the plating solution M1. In this example, at least the two in-solution rotary rollers 21 a and 21 b are used to improve running stability of the wire W and thus increase the running speed of the wire. Accordingly, it is possible to further increase the production speed by adjusting as appropriate the number of back-and-forth runs of the wire and the like. Alternatively, three in-solution rotary rollers may be arranged such that the total four rotary rollers each constitute the apexes of a square such as a lozenge in a lateral view, or the number of in-solution rotary rollers may be increased as necessary.

In this arrangement, as shown in FIGS. 8 and 9, it is preferred that the wire is first run once back and forth between the out-solution rotary roller 20 and the one in-solution rotary roller 21 a, and then is run once back and forth between the out-solution rotary roller 20 and the other in-solution rotary roller 21 b, and the runs are repeated in sequence. Accordingly, the wire W is alternately run around the rotary rollers 21 a and 21 b inside the plating solution M1. Thus, the wire and the abrasive grains contact an increased number of times, which enhances the efficiency of electrodeposition of abrasive grains.

FIG. 5 shows another modification example of a layout of rotary rollers in which two out-solution rotary rollers 20 a and 20 b and one in-solution rotary roller 21 are arranged. In this example, arranging the two out-solution rotary rollers outside the plating solution M1 makes it possible to disperse a stress applied to the running wire W and thus achieve more stable running of the wire. It is preferred to supply an electric current to both the out-solution rotary rollers 20 a and 20 b from the viewpoint of increasing the amount of an electric current applied to the wire W and maintaining the electric current density, but only one of the two rotary rollers may be supplied with an electric current.

It is preferred to provide a guide groove 7 for guiding the wire on the outer peripheral surfaces of the out-solution rotary roller 20 and the in-solution rotary roller 21 as shown in FIG. 11, from the viewpoint of attaining running stability of the wire and stable electric current supply to the wire. The guide groove 7 may be formed by a continuous spiral concave, or a plurality of link-shaped concaves arranged in the axial direction or the like, but the guide groove 7 is not limited to the foregoing ones.

The abrasive grain amount calculation means 4 includes a camera 40 that images the outer surface of the wire W running from the first plating tank 16A, and a control computer 6 that calculates the amount of the abrasive grains D adhered to the outer surface of the wire W based on image information obtained from the camera 40 as shown in FIGS. 2 and 6. The control computer 6 is connected to the camera 40 and the power feeding device 30. The control computer 6 serves as abrasive grain amount calculation means 4 to calculate the amount of abrasive grains based on image information received from the camera 40, and serves as electric current control means 5 to transmit to the power feeding device 30 a control signal for increasing or decreasing the value of an electric current flown into the wire W running through the first plating tank 16A to control variations in the amount of abrasive grains adhered to the outer surface of the wire in the first plating tank 16A so as to fall within a predetermined range.

The camera 40 may be positioned as appropriate between the first plating tank 16A and the second plating tank 16B, between the second plating tank 16B and the water washing tank 17, between the water washing tank 17 and the winding machine 18, or inside the first plating tank 16A. The number of the camera 40 is not limited to one but a plurality of cameras may be provided at predetermined intervals along the wire W, for example, to obtain a plurality of images in an efficient manner.

The control computer 6 includes a processing device 60 and a storage means 61 as shown in FIG. 3. The processing device 60 is connected to the power feeding device 30 and the camera 40. The processing device 60 is mainly formed by a CPU such as a microprocessor and is configured to have a storage part including a RAM and a ROM not shown to store programs describing procedures for various processes and processed data.

The processing device 60 includes functionally at least: an image information acquisition processing part 60 a that stores image information received from the camera 40 in an image information storage part 61 a of the storage means 61; an abrasive grain amount calculation processing part 60 b that calculates the amount of abrasive grains based on the image information stored in the image information storage part 61 a; a determination processing part 60 c that determines whether the amount of abrasive grains calculated at the abrasive grain amount calculation processing part 60 b falls within a preset predetermined range; and an electric current control processing part 60 d that generates a control signal for increasing or decreasing the value of an electric current according to results of the determination by the determination processing part 60 c and transmits the signal to the power feeding device 30. These functions are realized by the foregoing programs. The storage means 61 is formed by a hard disc or the like inside or outside the control computer 6. The storage means 61 includes at least the image information storage part 61 a storing the acquired image information. As a matter of course, the storage means 61 may store data in a temporary storage region, not in the foregoing hard disc or the like.

The image information acquisition processing part 60 a may acquire successively image data continued for a short time from the camera 40, may acquire image data continued for a short time for a predetermined number of images at predetermined time intervals, may acquire one piece of image data at predetermined time intervals, or may acquire image data in any other form. FIG. 4 (a) is a schematic view of a region 62 of the wire W with the abrasive grains D adhered via a first plating layer ml imaged by the camera 40. FIGS. 4 (b) to 4 (d) show examples of image information acquired by the image information acquisition processing part 60 a and stored in the image information storage part 61 a of the storage means 61.

The abrasive grain amount calculation processing part 60 b calculates the amount of abrasive grains in the numerical values of number, area ratio, and the like of abrasive grains, based on the image information stored in the image information storage part 61 a. The number and area ratio of abrasive grains may be calculated by recognition of abrasive grains included in the entire image information or a predetermined region of the image information, or may be calculated by recognition of projecting portions in appearance or with a predetermined height or more in the region as shown in FIG. 5, or may be calculated as a numerical value reflecting the amount of adhered abrasive grains. In this example, as shown in FIGS. 4 (b) to 4 (d), the numbers or area ratios of abrasive grains obtained from a plurality of image information are summed up, and the summed value or the average value is calculated as amount of abrasive grains. As a matter of course, as described above, it is possible to convert a plurality of image information (a) to (c) to shape recognition data (a′) to (c′) in which projecting portions with a predetermined height or more are recognized, and calculate the summed value or average value of these portions as amount of abrasive grains, as shown in FIG. 5.

The determination processing part 60 c determines whether the amount of abrasive grains calculated at the abrasive grain amount calculation processing part 60 b, for example, the summed value of number of abrasive grains falls within a preset predetermined numerical range. When the determination processing part 60 c determines that the summed value, for example, exceeds the upper limit in the numerical range, the electric current control processing part 60 d calculates the amount of an electric current to be decreased according to the magnitude of the exceeding value by a predetermined equation, and generates a control signal for decreasing the electric current and transmits the same to the power feeding device 30. In reverse, when the summed value falls below the lower limit, the electric current control processing part 60 d calculates the amount of an electric current to be increased according to the magnitude of the underrunning value by a predetermined equation, and generates a control signal for increasing the electric current and transmits the same to the power feeding device 30. Alternatively, specific amounts of an electric current to be increased and decreased may be decided in advance, instead of calculating the same by the equations.

The second plating tank 16B is almost the same in configuration as the first plating tank 16A, except that no abrasive grains are contained in a plating solution M2. The wire W is run back and forth a plurality of times between the two rotary rollers 20 and 21 inside and outside the plating solution M2, an electric current is supplied to the out-solution rotary roller 20 and the in-solution anodes. Then, the wire fed from the first plating tank 16A and having abrasive grains adhered to the outer surface via the first plating layer is further subjected to second plating to form a second plating layer on the outer surface of the wire by electroplating. To form the second plating layer that is thicker than the first plating layer and is uniform in thickness as much as possible, the value of a supplied electric current is preferably kept constant to maintain the constant electric current density for realizing a homogenous plating thickness on the entire saw wire. Preferably, the thickness of the first plating layer is adjusted to 30% or less of the entire plating thickness including the second plating layer.

As described above, in this example, the wire is routed around and run back and forth a plurality of times between the out-solution and in-solution rotary rollers 20 and 21 in both the first plating tank 16A and the second plating tank 16B. Alternatively, the foregoing configuration may be made only in one of the plating tanks such that the other plating tank is formed in a conventionally public-known general mode in which no wire is run back and forth. Accordingly, it is possible to enhance production efficiency in such a manner that the first plating tank 16A is formed in the foregoing general mode and the second plating tank 16B is formed in a mode in which the wire is run back and forth as described above, and the opposite is possible.

As in the foregoing, embodiments of the present invention are described. However, as a matter of course, the present invention is not limited to these examples but can be carried out in various manners without deviating from the gist of the present invention. 

1. A method for manufacturing an abrasive grain-fixed saw wire by which a wire is passed through a plating solution containing abrasive grains to fix the abrasive grains to the outer periphery of the wire by electroplating, wherein the amount of the abrasive grains adhered to the outer surface of the wire having passed through the plating solution is calculated, and based on the calculated amount of the abrasive grains, the value of an electric current flown into the wire in the plating solution is increased or decreased to control variations in the amount of abrasive grains adhered to the outer surface of the wire so as to fall within a predetermined range.
 2. The method for manufacturing a saw wire according to claim 1, wherein, after forming the wire with the abrasive grains adhered to the outer surface by electroplating via a first plating layer, the wire is passed through a plating solution without abrasive grains to form a second plating layer on the outer surface by electroplating.
 3. The method for manufacturing a saw wire according to claim 2, wherein the first plating layer for adhering the abrasive grains to the outer surface of the wire is configured to be thinner than the second plating layer.
 4. The method for manufacturing a saw wire according to claim 1, wherein the outer surface of the wire having passed through the plating solution is imaged by a camera, and the amount of the abrasive grains is calculated based on image information in the taken image.
 5. The method for manufacturing a saw wire according to claim 1, wherein the wire is routed around a plurality of times between an out-solution rotary roller that is disposed outside the plating solution and supplied with an electric current by an electric current supply means and an in-solution rotary roller that is disposed in the plating solution, and the wire is run back and forth a plurality of times between inside and outside of the plating solution.
 6. The method for manufacturing a saw wire according to claim 5, wherein the wire is routed around at least two in-solution rotary rollers disposed in the plating solution.
 7. The method for manufacturing a saw wire according to claim 5, wherein a guide groove for guiding the wire a plurality of times in the direction of roller circumference, is provided on the outer peripheral surface of the out-solution rotary roller and/or the in-solution rotary roller.
 8. The method for manufacturing a saw wire according to claim 1, wherein the plating solution is stirred by a stirring means disposed in the plating solution.
 9. A device for manufacturing an abrasive grain-fixed saw wire that lets a wire pass through a plating solution containing abrasive grains to fix the abrasive grains to the outer periphery of the wire by electroplating, comprising: a plating tank that stores the plating solution containing the abrasive grains; a wire feeding means that lets the wire pass through the plating solution; an electric current supply means that supplies an electric current to the wire and the plating solution; an abrasive grain amount calculation means that calculates the amount of abrasive grains adhered to the outer surface of the wire having passed through the plating solution; and an electric current control means that increases or decreases the value of an electric current flown into the wire in the plating solution by the electric current supply means according to the amount of abrasive grains calculated by the abrasive grain amount calculation means to control variations in the amount of the abrasive grains adhered to the outer surface of the wire so as to fall within a predetermined range.
 10. The device for manufacturing a saw wire according to claim 9, wherein the abrasive grain amount calculation means includes a camera that images the outer surface of the wire having passed through the plating solution and a computing means that calculates the amount of the abrasive grains based on image information in an image taken by the camera.
 11. The device for manufacturing a saw wire according to claim 9, comprising an out-solution rotary roller that is disposed outside the plating solution and supplied with an electric current by the electric current supply means and an in-solution rotary roller that is disposed in the plating solution, wherein the wire is routed around a plurality of times between the out-solution rotary roller and the in-solution rotary roller and is run back and forth a plurality of times between inside and outside of the plating solution. 